The present invention relates to tilt sensors and, more particularly, to a tilt sensor usable for sensing the inclination or acceleration of a vehicle.
Tilt sensors are devices used to measure angular displacement of a vehicle or structure relative to a reference. Tilt sensors are used in a wide variety of industrial and transportation applications for measuring inclinations and accelerations.
Tilt sensors used to detect angular inclination or displacement with respect to a horizontal reference are known as inclinometers. The reference is typically supplied by the gravitational pull of the earth. Inclinometers typically comprise a fixed element that is rigidly mounted to a piece of equipment whose inclination is to be measured, a reference element that maintains a constant orientation with respect to a reference, a sensor that measures the angular displacement between the fixed and reference elements, and a suspension system that supports the reference element while allowing relative rotation between the elements.
In existing inclinometer designs, the sensing technologies and methods for suspending the reference element within the fixed element are relatively complex and expensive. For example, a gyroscopic inclinometer relies on the angular momentum vector of a rapidly rotating mechanical part to provide a reference orientation. Gyroscopic inclinometers require a mechanically complex suspension for the rotating part and are, therefore, expensive.
Inclinometers that utilize a suspended pendulum as the reference element rely on gravity to maintain a reference orientation, typically using a suspension system including bearings that allow the pendulum to continue to point downward as the orientation of the fixed element changes. Suspension systems utilizing bearings that allow rotation of the pendulum in more than one axis are also complex and expensive.
Capacitive inclinometers typically utilize conductive plates as part of the fixed element. The reference element is located between the plates of the fixed element. Changing the angular displacement of the reference element with respect to the plates changes the dielectric constant of the space between, and therefore the capacitance of, the plates. The change in capacitance is detected and converted to a corresponding tilt angle. Capacitive inclinometers typically require relatively complex circuitry to convert the change in capacitance to a corresponding change in tilt angle and a relatively complex mechanical suspension system to maintain the reference element between the plates without touching the plates.
Because of the relative complexity of sensing technologies and of methods for suspending the reference element within the fixed element, existing inclinometers are relatively costly and their use is usually restricted to industrial applications.